Microstructure control in two-phase Al–21Ti–23Cr alloy

To improve the mechanical properties of the Al–21Ti–23Cr two-phase alloy consisting of L12 matrix and 20 vol% Cr2Al as a second phase, microstructure control was conducted through the aging treatment as a thermal process and the addition of V and Zr as conventional alloying. It was found that TiAlCr was precipitated as a third phase in the L12 matrix by the aging treatment at 800 and 1000°C, and its size was smaller at 800°C than at 1000°C. The yield strength of the aged alloy increased rapidly only at 800°C although the third phase was precipitated at both 800 and 1000°C. In the V-added two-phase alloys, the yield strength and the strain increased simultaneously when V was added up to 3 at%, which is attributable to the improvement in the ductility of Cr2Al. Microstructure control conducted in this study suggests the possibility of improving the mechanical properties of L12 (Al,Cr)3Ti-based two-phase alloy by precipitating the fine third phase in the L12 matrix and enhancing the ductility of the second phase.